Inking unit for a printing machine and method for supplying ink to a printing machine

Abstract

An inking unit for a printing machine includes one or more distributor drums, ink transfer rollers, ink application rollers, an ink reservoir for printing ink and an ink metering device having at least one electrically controllable valve for metering the printing ink. In accordance with the invention, there are provided a high-pressure pumping device for supplying the ink metering device with printing ink at a predetermined high pressure from the ink reservoir, and a heating device for heating the printing ink to a predetermined temperature above room temperature. Moreover, the at least one valve of the ink metering device has a short reaction time and a flow rate with a low dependence upon viscosity. The invention also relates to a method for supplying printing ink to a printing machine.

I claim:  
     
       1. In combination with a printing press, an inking unit comprising: 
       an ink metering device having at least one electrically controllable valve with a short reaction time for precisely metering the printing ink and with an ink flow rate substantially independent of viscosity of the printing ink;  
       a high-pressure pumping device for supplying the printing ink metering device with printing ink at a predetermined high pressure; and  
       a heating device for heating the printing ink to a predetermined temperature above room temperature.  
     
     
       2. The inking unit according to  claim 1 , wherein the at least one valve includes piezoelectric actuators. 
     
     
       3. The inking unit according to  claim 1 , wherein the at least one valve includes a spherical sealing element disposed opposite a spherically recessed valve seat wherein an opening having a substantially smaller diameter than that of said spherical sealing element is formed. 
     
     
       4. The inking unit according to  claim 1 , wherein the printing ink, at room temperature and a low shear rate, has a dynamic viscosity of more than 10 pascal seconds, said pumping device being capable of producing a pressure in the range of approximately 10 to 100 bar, and the temperature of the printing ink heated by the heating device being in a range of approximately 40° C. to 70° C. 
     
     
       5. The inking unit according to  claim 1 , wherein said ink metering device includes a row of nozzles directed onto the surface of a distributor drum. 
     
     
       6. The inking unit according to  claim 1 , further comprises at least one ink zone, and a respective valve for each ink zone, said respective valve having an outlet connected to said at least one nozzle disposed in the respective ink zone. 
     
     
       7. The inking unit according to  claim 1 , further comprising an ink reservoir for supplying the printing ink metering device with printing ink via said high-pressure pumping device. 
     
     
       8. The inking unit according to  claim 1 , including a valve for supplying cleaning liquid for cleaning the ink metering device. 
     
     
       9. The inking unit according to  claim 8 , wherein the ink metering device is provided for spraying cleaning liquid onto a distributor drum through the at least one valve of the ink metering device. 
     
     
       10. The inking unit according to  claim 7 , wherein said ink reservoir is an ink cartridge or a bulk container. 
     
     
       11. A method for supplying printing ink to a printing press, which comprises: 
       feeding printing ink to at least one valve at a predetermined high pressure and at a predetermined temperature above room temperature; and  
       metering the printing ink by at least one electrically controllable valve in accordance with the demand of the printing press free of excessive metering of ink.  
     
     
       12. The method according to  claim 11 , which includes providing a printing ink which, at room temperature and a low shear rate, has a dynamic viscosity of more than 10 pascal seconds, pressurizing the printing ink in the range of approximately 10 to 100 bar, and heating the printing ink to a temperature in the range of approximately 40° to 70° C. 
     
     
       13. The method according to  claim 11 , wherein the at least one valve has a reaction time in the order of magnitude of microseconds, and which includes metering the ink by opening and closing the at least one valve under pulse-length control. 
     
     
       14. The method according to  claim 11 , wherein the printing press has a machine time cycle with a distributor stroke, a distributor revolution, and a distributor drum having a stroke and being revolvable, and the method further comprises the step of spraying the printing ink out of synchronism with the machine time cycle onto the distributor drum of the printing press so that, with one of each distributor stroke and each distributor revolution, respectively, the printing ink is applied offset temporally relative to the machine time cycle. 
     
     
       15. The method according to  claim 11 , which further comprises performing the step of metering the printing ink using a piezoelectric actuator. 
     
     
       16. In combination with a printing press, an inking unit comprising: 
       at least one electrically controllable valve with a short reaction time;  
       a high-pressure pumping device for supplying the printing ink to the valve at a predetermined high pressure;  
       a heating device for heating the printing ink to a predetermined temperature above room temperature;  
       said at least one valve, said high-pressure pumping device, and said heating device cooperating for precisely metering and uniformly spraying printing ink substantially independently of the viscosity of the printing ink.  
     
     
       17. An inking unit for a printing machine, comprising: 
       at least one electrically controllable valve with a short reaction time;  
       a high-pressure pumping device for pressurizing a printing ink in the range of approximately 10 to 100 bars and supplying the printing ink to the valve at a predetermined high pressure; and  
       a heating device for heating the printing ink to a temperature in the range of approximately 40° to 70° C.;  
       said at least one valve, said high-pressure pumping device, and said heating device co-operating for precisely metering and uniformly spraying the printing ink substantially independently of the viscosity of the printing ink.  
     
     
       18. The inking unit according to  claim 17 , wherein the at least one valve includes piezoelectric actuators. 
     
     
       19. The inking unit according to  claim 17 , wherein the at least one valve includes a spherical sealing element disposed opposite a spherically recessed valve seat, forming an opening having a substantially smaller diameter than that of said spherical sealing element. 
     
     
       20. A method for supplying printing ink to a printing machine, which comprises: 
       feeding printing ink to at least one valve at a pressure in the range of approximately 10 to 100 bar and at a temperature in the range of approximately 40° to 70° C.; and  
       metering the printing ink by at least one electrically controllable valve in accordance with the demand of the printing machine free of excessive metering of ink.  
     
     
       21. The method according to  claim 20 , wherein the at least one valve has a reaction time in the order of magnitude of microseconds, and which further comprises metering the ink by opening and closing the at least one valve under pulse-length control. 
     
     
       22. The method according to  claim 20 , wherein the printing machine has a machine time cycle with a distributor stroke, a distributor revolution, and a distributor drum having a stroke and being revolvable, and the method further comprises the step of spraying the printing ink out of synchronism with the machine time cycle onto the distributor drum of the printing machine so that, with one of each distributor stroke and each distributor revolution, respectively, the printing ink is applied offset temporally relative to the machine time cycle. 
     
     
       23. The method according to  claim 20 , which further comprises performing the step of metering the printing ink using a piezoelectric actuator.